A conventional trend graph display apparatus displays a measured value of a most recent 24 hours along a time axis from 0 o'clock to 24 o'clock in a line graph. The trend graph display apparatus displays a current position line at a graph point that indicates a current measured value, and a blank space is provided between a current graph point and a graph point of 24 hours ago. The current position line and the blank space facilitate easier recognition of a change in the measured value of the most recent 24 hours (Patent Literature 1).
With the conventional technology, however, a change in a measured value before the most recent 24 hours is unable to be recognized. For example, when current time is 12 o'clock, a measured value from 0 o'clock to 12 o'clock of a day before is unable to be recognized with the conventional technology. Therefore, it is difficult to compare the change in the measured value of the day before with the change in the measured value of the current day.